This invention relates generally to combustion turbine engines, and, in particular, to cooling of turbine fluid guide members.
In a typical combustion turbine engine, a variety of vortex flows are generated around airfoil elements within the turbine. FIG. 1 is a perspective view of a cut-away of several turbine airfoil portions 1 showing hot combustion fluid flow 3 around the airfoil portions 1. It is known that xe2x80x9chorseshoexe2x80x9d vortices, including a pressure side vortex 4, and a suction side vortex 5, are formed when a hot combustion fluid flow 3 collides with the leading edges 6 of the airfoil portions 1. The vortices 4,5 are formed according to the particular geometry of the airfoil portions 1, and the spacing between the airfoil portions 1 mounted on the platform 2. As the hot combustion fluid flow 3 splits into the pressure side vortex 4 and a suction side vortex 5, the vortices 4,5 rotate in directions that sweep downward from the respective side of the airfoil portion 1 to the platform 2. On the pressure side 8 of the airfoil portions 1, the pressure side vortex 4 is the predominant vortex, sweeping downward as the pressure side vortex 4 passes by the airfoil portion 1. As shown, the pressure side vortex 4 crosses from the pressure side 8 of the airfoil portion 1 to the suction side 7 of an adjacent airfoil portion 1. In addition, the pressure side vortex 4 increases in strength and size as it crosses from the pressure side 8 to the suction side 7. Upon reaching the suction side 7, the pressure side vortex 4 is substantially stronger than the suction side vortex 5 and is spinning in a rotational direction opposite from the suction side vortex 5. On the suction side 7, the pressure side vortex 4 sweeps up from the platform 2 towards the airfoil portion 1. Consequently, because the pressure side vortex 4 is substantially stronger that the suction side vortex 5, the resultant, or combined flow of the two vortices 4, 5 along the suction side 7 is radially directed to sweep up from the platform 2 towards the airfoil portion 1.
A conventional approach to cooling fluid guide members, such as airfoils in combustion turbines, is to provide cooling fluid, such as high pressure cooling air from the intermediate or last stages of the turbine compressor, to a series of internal flow passages within the airfoil. In this manner, the mass flow of the cooling fluid moving through passages within the airfoil portion provides backside convective cooling to the material exposed to the hot combustion gas. In another cooling technique, film cooling of the exterior of the airfoil can be accomplished by providing a multitude of cooling holes in the airfoil portion to allow cooling fluid to pass from the interior of the airfoil to the exterior surface. The cooling fluid exiting the holes form a cooling film, thereby insulating the airfoil from the hot combustion gas. While such techniques appear to be effective in cooling the airfoil region, little cooling is provided to the fillet region where the airfoil is joined to a mounting platform.
The fillet region is important in controlling stresses where the airfoil is joined to the platform. Although larger fillets can lower stresses at the joint, such as disclosed in U.S. Pat. No. 6,190,128, the resulting larger mass of material is more difficult to cool through indirect means. Accordingly, prohibitively large amounts of cooling flow may need to be applied to the region of the fillet to provide sufficient cooling. If more cooling flow for film cooling is provided to the airfoil in an attempt to cool the fillet region, a disproportionate amount of cooling fluid may be diverted from the compressor system, reducing the efficiency of the engine and adversely affecting emissions. While forming holes in the fillet to provide film cooling directly to the fillet region would improve cooling in this region, it is not feasible to form holes in the fillet because of the resulting stress concentration that would be created in this highly stressed area.
Backside impingement cooling of the fillet region has been proposed in U.S. Pat. No. 6,398,486. However, this requires additional complexity, such as an impingement plate mounted within the airfoil portion. In addition, the airfoil portion walls in the fillet region are generally thicker, which greatly reduces the effectiveness of backside impingement cooling.
Accordingly, there is a need for improved cooling in the fillet regions of turbine guide members.
A turbine fluid guide member is described herein as including: an airfoil portion; a platform portion; and a fillet joining the airfoil portion to the platform portion. The turbine fluid guide member also includes a coolant outlet positioned remotely from the fillet such that a cooling flow exiting the outlet is directed by a vortex flow to form a cooling film over the fillet. In addition, the turbine fluid guide member may include a plurality of holes formed in the airfoil directing a coolant flow into a vortex flow to create a cooling film along a portion of the fillet on the pressure side. The turbine fluid guide member may also include another plurality of holes formed in the platform directing the coolant flow into a vortex flow to create another cooling film along a portion of the fillet on the suction side.
A combustion turbine engine is described herein as including: a compressor; a turbine; a combustor; and a turbine fluid guide member. The turbine fluid guide member also includes an airfoil portion, a platform portion, a fillet joining the airfoil portion to the platform portion, and a coolant outlet positioned remotely from the fillet such that a cooling flow exiting the outlet is directed by a vortex flow to form a cooling film over the fillet.
A method for cooling a portion of a turbine fluid guide member is described herein as including: identifying a vortex flow around the turbine fluid guide member; and selectively positioning a coolant outlet relative to the vortex flow such that a cooling flow exiting the outlet is directed by the vortex flow to form a cooling film over a fillet portion of the turbine fluid guide member.